A's designated hitter Seth Smith and Tigers starter Anibal Sanchez watch Smith's two-run homer in the fifth inning. The blast chased Sanchez, the American League ERA leader, from the game and gave the A's a 6-3 lead.

He wasn't. Designated hitter Seth Smith had one more duty before leaving Comerica Park: rush from the clubhouse to the field to defend his teammates, or mix it up if need be.

"It was already over when I got out there," Smith said.

Moments later, it was really over, the A's beating the Tigers 6-3, thanks in large part to Smith, who was a forgotten man in September but is front and center in October. He had the least talked-about hit in Game 2 and the most talked-about hit in Game 3, both contributing to A's wins.

Smith's two-run homer in the fifth inning Monday chased Tigers starter Anibal Sanchez and gave the A's a comfortable three-run lead. In Game 2, his ninth-inning single was sandwiched between singles by Yoenis Céspedes and Stephen Vogt, Vogt's hit scoring Céspedes to end it.

Smith, 4-for-8 in the Division Series, sat out the opener (which Oakland lost), prompting Josh Reddick to say in retrospect, "He doesn't start Game 1, and it kind of makes you wonder what he could've done with that start."

After getting shut down by Max Scherzer and Justin Verlander, the A's had far better success against Sanchez, the American League's ERA leader and every bit the strikeout fiend as Scherzer and Verlander. The difference: The A's got to Sanchez for eight hits, including three home runs.

Reddick and Brandon Moss joined Smith, all lefty swingers, in playing Home Run Derby. The first two pulled pitches into the right-field seats. Smith sent his to left-center, continuing to torment Sanchez, against whom he's 9-for-22 with four home runs.

He was the odd man out for much of the season. After the A's acquired Chris Young, they had four quality defensive outfielders. Smith was the fifth outfielder, which guaranteed nothing but solidifying his role as a part-time DH, which he assumed when the A's acquired him from the Rockies before the 2012 season.

In September, with Céspedes serving as DH while mending his sore shoulder, Smith hardly played. He started just seven games but made the most of it, hitting .393 with a .469 on-base percentage.

"In my career, I've had practice at not playing for a while and then playing," Smith said. "It's the big leagues. Especially now in the postseason, you're expected to get the job done, regardless of what you're asked to do."

It helps that he can see the ball. Smith, who had Lasik surgery early in his career, had some follow-up work in August, and it made a difference. Beforehand, he scuffled through a 40-game stretch in which he hit .189.

"I see better. You hit better when you can see better," Smith said.

He's not alone, especially in Detroit. The A's scored 34 runs in a four-game series at Comerica in late August, and after Monday's offensive outburst, Moss said, "We all seem to agree we see the ball much better here. That's going to help a hitter out."

This is Smith's fourth postseason, including with the 2007 Rockies, who were swept by Boston in the World Series. He broke into the majors that September and was a pinch-hitter in October. This time around, he's contributing in a far greater way.

His homer provided breathing room for relievers Dan Otero, Sean Doolittle and Balfour, who combined for four shutout innings.

As DH, Smith had retreated to the clubhouse in the final inning but made a beeline for the field once he noticed on television that players and coaches were streaming in from the benches and bullpens.

He was late. Fortunately for the A's, he was inserted into their lineup just in time.